Why do sponge cakes become hard in cold weather?

Sponge cakes can become hard in cold weather due to a combination of factors, including changes in humidity and temperature that affect the cake's moisture content. When exposed to colder air, the moisture in the cake can evaporate more quickly, leading to a drier texture. Additionally, the fats in the cake may solidify, contributing to a firmer structure. Proper storage, such as covering the cake or keeping it in a sealed container, can help maintain its softness.